High speed filling lines are commonly used to fill a variety of containers of various shapes and sizes. The machinery typically positions the receiving container for the product in alignment with a fill nozzle or outlet. After the product is delivered, a closure is put on to seal the bottle. The capping machinery has controls built in that are used in placement of the closure. In order to assure rapid and secure placement of the closure, the equipment needs to be able to deliver certain forces and torques to secure the closure. For closures that secure by snap or interference fit, there is a balance that needs to be drawn between getting a secure slip free contact between the container and the closure and the limits of the machinery to deliver the desired force and keep the filling line moving at the desired speed. If the clearances are too tight the resulting required forces can get too high for the capping equipment. This can result in an incomplete placement of the closure on the container and potential product leakage along the distribution chain.
FIGS. 1-6 illustrate this problem in a prior art bottle that uses a snap fit closure onto the neck of an elongated bottle. Referring to FIG. 1, the bottle 10 has a neck generally indicated at 12 at its top end. A support ring 14 defines the beginning of the neck 12 and features an upwardly oriented shoulder 16. A ring 18 located above support ring 14 defines an undercut radial surface 20. Above ring 18 and working up to the top of the neck 12 are a pair of transition surfaces 22 and 24 that ultimately lead to the top 26 of the neck 12. The closure 28 is shown above the bottle 10 in the position that the capping machinery would hold it before driving it home onto the neck 12. Closure 28 has an outer surface 30 and an inner surface 32. Inner surface 32 has a series of circumferentially spaced inwardly oriented projections 34 that each features a radial surface 36 adjacent a tapered and downwardly extending surface 38. Inner surface 32 also features a longitudinally extending and generally rectangular shaped key 40 having a taper 42 at its lower end. A ring 44 is disposed concentrically to inner surface 32 and has a gradual exterior outward taper 46. Neck 12 further comprises a longitudinally oriented gap 48 which is wider than key 40, for reasons that will be explained below. Closure 28 has an outlet 50 which can be any known design for getting the product out of the bottle 10 when it is placed in use.
With the components now having been described, the process of assembling the closure 28 to the bottle 10 will now be described and in the process, its limitations will be more readily understood. Those skilled in the art will appreciate that the machinery that is not shown receives a closure 28 in a random orientation with regard to the location of key 40. Stated differently, key 40 may or may not be axially aligned with gap 48 when the closure 28 is brought down on the neck 12. Comparing FIGS. 1 and 2, it can be seen that the closure 28 has been brought closer to the neck 12 and that closure 28 has been rotated about its vertical axis to change the orientation of the key 40 with respect to the gap 48. In FIG. 2, they are in further misalignment than they were in FIG. 1. FIG. 3 compared to FIG. 2 shows further downward movement of closure 28 as well as a further rotation of about 90° about its vertical axis as compared to the FIG. 2 position. In FIG. 3, tapered surface 38 has landed on transition surface 22 of neck 12. Taper 42 at the lower end of key 40 has landed on tapered surface 25 just below the top 26 of the neck 12. It is apparent that key 40 is still misaligned with gap 48 in this position. Tapered surface 46 of ring 44 is inside the top end 26 and on the verge of contact with the inside wall of the neck 12. Now comparing FIG. 4 to FIG. 3, the closure 28 has been pushed further down but not rotated by much. At this point radial surface 36 has been snapped to below radial surface 20. Tapered surface 46 of ring 44 is now in contact with the inside surface of the neck 12 just below end 26. Key 40 is now straddling ring 18. Those skilled in the art will appreciate that subsequent effort to rotate the closure 28 after being forced down to the FIG. 4 position will engender significant resistance from several contact points with neck 12. The key 40 extending over ring 18 will resist rotation as will the rubbing of ring 44 inside the upper end 26 of the neck 12. Finally, there is an upward force that forces radial surface 36 of closure 28 up against radial surface 20 of ring 18 on the neck 12. This residual force results from the dimensions of the components and the driving of the closure 28 down over ring 18. The problem in the past with this design is that the equipment is either torque limited or has settings that limit applied torque to the closure 28 to avoid component damage by forcing a fit in situations where the components may not be totally in axial alignment. The compound effect of these interference fits that are desirable in assuring the securing of the closure 28 to the bottle 10 become a disadvantage during the filling process. Comparing now FIG. 5 to FIG. 4, it can be seen that the closure is rotated about its longitudinal axis to bring key 40 closer to gap 48. The assembly is finished when key 40 snaps off ring 18 and settles into gap 48 to rotationally lock the closure 28 to the neck 12.
The present invention improves the configuration of the components to greatly reduce the required torque to assemble them while, in the end, allowing them to be securely connected to each other as in the past. One way this is accomplished is an emphasis on getting the components into their final alignment positions at a time when less interference contact exists, thus greatly reducing the required torque for rotating the closure into its final position. In the end the closure is just as secure as in the prior art design but the assembly process has been optimized in view of the low applied torque required to reach the final made up position of the components. These and other advantages of the present invention will more readily be understood by those skilled in the art from a review of the remaining drawings and the associated description of the preferred embodiment as well as the claims for the invention that appear below.